When I am connecting my hard disk to my laptop, files are not visible. They are showing hidden in my friend’s laptop. So I made the hidden files appear on my [friend’s ???] laptop. Even after that, they are not visible. Please help me!
If I understand your description correctly, the files are hidden, and on your friend's laptop you were able to show them. You would need to do the same on your own laptop in order to see them, since this is a per-PC option (i.e. it does not "travel with the files"). In Windows 7, open "My Computer", Organise=>Folder and Search Options, /View and tick "Show hidden files, folders and drives". Hopefully, this addresses your immediate question.
That said, why are the files hidden? Ordinary data files should not be hidden, so unless you chose to hide them, something is amiss. You can follow Hovsep's instructions to remove the "-hidden" attribute from the files, but you should still be concerned about how they became hidden in the first place. I'd suggest scanning your PC for viruses and spyware just to be sure there's nothing malicioius running in the background.
the scan for malware should be done on friends laptop and later when the hard drive is plugged to his own pc better to scan again the external hard drive.
You may also be looking at a permissions issue. If the Everyone group does not have access to the root directory of the drive, then files will only be accessible on the machine that has the GUID for any other users who were given access to the drive.
The globally unique numeric identifiers that are used for users and groups on Windows systems are built up out of 2 parts. The first part is a globally unique identifer for the machine itself followed by what amounts to a user or group number for the users and groups on the machine. It looks like there is an exception for the Everyone group in that it does either does not have the machine portion of the ID or it just ignores it. So if the Everyone group is not there, all other allowed users and groups are tied to the machine that formatted the drive (and saved files and folders there) and any other machine attempting to access the files and folders on the drive will be denied access. (You cannot even list the files and folders on the device since you are not a user that has the requisite permissions to do so on the drive.)
1) Start -->Run-->type cmd, right click on it and choose run as administrator
2) if your hard drive as G:
3) Enter this command: attrib -h -r -s /s /d g:*.*
4) Then check if your real files will be shown